Hydrating swellable clays

ABSTRACT

A treatment fluid may comprise: a water having hardness at about 300 ppm or greater, a plurality of particulates, a swellable clay, a chelating agent at about 0.01% to about 5% by weight of the water (BWOW); and an alkali metal base at about 0.01% to about 5% BWOW, wherein the chelating agent and alkali metal base reduce the negative effect of the water on hydrating swellable clays.

BACKGROUND

Embodiments of the present disclosure relate to hydrating swellableclays.

Treatment fluids used in various downhole operations (e.g., drillingoperations, cementing operations, and workover operations) may beviscosified with swellable clays that assist in maintaining particulatessuspended in the treatment fluid. However, when preparing treatmentfluids with saltwater or hard water, the chloride ion concentration ordissolved mineral concentration, respectively, have resulted in settlingout of the clay and development of viscosities of only a smallpercentage of those which would result if fresh water were used. Withoutbeing limited by theory, the flocculation and lack of viscositydevelopment may be due to the lessening of interparticle forces betweenthe clay particles.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of theembodiments and should not be viewed as exclusive embodiments. Thesubject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, as willoccur to those skilled in the art and having the benefit of thisdisclosure.

FIG. 1 shows an illustrative schematic of a system that can delivertreatment fluids of the present disclosure to a downhole location.

FIG. 2 shows an illustrative schematic of a drilling system forimplementing a drilling fluid and/or drill-in fluid described herein.

FIG. 3 is an on-off thickening plot for a cement sample.

FIG. 4 is an ultrasonic cement analysis plot for a cement sample.

FIG. 5 a static gel strength plot for a cement sample.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate to hydrating swellableclays dispersed in water having a high hardness (i.e., hard water). Insome instances, the swellable clays may be a part of a cement slurryproduced with a hard water.

As used herein, the term “hard water” refers to water with dissolvedcalcium and magnesium. As used herein, the term “hardness” refers to theamount of dissolved calcium and magnesium in the water.

Swellable clay may be used to thicken or viscosify a treatment fluid,which aids in maintaining the particles (e.g., weighting agent, cementparticles, and fillers) therein in suspension. Typically, when swellableclays are added to the treatment fluid, the water hydrates the claycausing it to swell and, consequently, viscosify the treatment fluid.Ions present in the water can lead to the clay not swelling to full sizeor not swelling at all. For example, water with a hardness of less than300 ppm hydrates clays like bentonite sufficiently. Above that hardness,the amount of clay swelling can be significantly reduced.

Embodiments of the present disclosure use a combination of a chelatingagent and an alkali metal base, each in relatively low concentrations,to synergistically reduce the negative impact of hard water on hydratingswellable clays. For example, as described further herein, at a hardnessof 700 ppm or greater, using only 0.2% chelating agent by weight ofwater (BWOW) in combination with 0.1% alkali metal base BWOW canincrease the gel strength of a cement slurry prepared with swellableclay by over 4 times within 10 minutes as compared to using either aloneat higher concentrations.

As used herein, the term “gel strength” refers to a measure of theability of a fluid to develop and retain a gel form. Gel strength ismeasured by the American Petroleum Institute recommended procedure 10B-6and, generally, is the shear stress measured at a low shear rate after afluid has set quiescently for 10 second, 10 minutes, or other identifiedtime period. Unless otherwise specified, as used herein, gel strengthmeasurements refer to 10 minute gel strength measurements.

Treatment fluids of the present disclosure may be produced by mixingwater having hardness of 300 ppm to 6000 ppm with a plurality ofparticulates, a swellable clay, a chelating agent at about 0.01% toabout 5% by BWOW, and an alkali metal base at about 0.01% to about 5%BWOW.

In some embodiments, the treatment fluids of the present disclosure maybe drilling fluids or drill-in fluids where the plurality ofparticulates comprises weighting agents and optionally cement. In someembodiments, the treatment fluids of the present disclosure may bedrilling fluids or drill-in fluids where the plurality of particulatescomprises weighting agents and optionally cement. In some embodiments,the treatment fluids of the present disclosure may be fracturing fluidswhere the plurality of particulates comprises proppant and optionallyweighting agents. In some embodiments, the treatment fluids of thepresent disclosure may be cement slurries where the plurality ofparticulates comprises cement and optionally proppants and/or weightingagents. In some embodiments, the treatment fluids of the presentdisclosure may be gravel-packing fluids where the plurality ofparticulates comprises gravel and optionally weighting agents.

Accordingly, exemplary particulates may include, but are not limited to,cement, weighting agent, proppant, gravel, and the like. Exemplarycements may include, but are not limited to, perlite, cement kiln dust,fly ash, pumicite, slag, lime, shale, Portland cement, and the like, andany combination thereof. Exemplary Portland cements may include, but arenot limited to, Class A, Class C, Class H, Class G, ASTM Type III, ASTMType V, and the like, and any combination thereof. In some embodiments,the particles are present at about 10% to about 300% BWOW.

Exemplary weighting agents may include, but are not limited to, barite,hematite, ilmentite, manganese tetraoxide, galena, calcium carbonate,and the like, and any combination thereof. In some embodiments, theweighting agent is present at about 1% to about 70% by volume of thetreatment fluid. In some instances, a sufficient concentration ofweighting agent may be used to achieve a treatment fluid with a densityof about 9 pounds per gallon (“lb/gal”) to about 22 lb/gal.

Exemplary proppants and gravels may include, but are not limited to,sand, bauxite, ceramic materials, glass materials, polymer materials,polytetrafluoroethylene materials, nut shell pieces, cured resinousparticulates comprising nut shell pieces, seed shell pieces, curedresinous particulates comprising seed shell pieces, fruit pit pieces,cured resinous particulates comprising fruit pit pieces, wood, compositeparticulates, and the like, and any combination

Exemplary swellable clays may include, but are not limited to,beidellite, montmorillonite, bentonite, nontronite, saponite, naturallyoccurring hectorite clay, synthetic hectorite clay, palygorskite,lasallite, and the like, and any combination thereof. In someembodiments, the swellable clay is present at about 0.1% to about 30%BWOW.

Exemplary chelating agents may include, but are not limited to,ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid,diethylenetriaminepentaacetic acid,trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid, citric acid,diglycolic acid, phosphoric acid, aspartic acid, tripolyphosphate,hexametaphosphate, aminotris (methylenephosphonic acid),1-hydroxyethane-1,1-diphosphonic acid, dimethyl methylphosphonate,ethylenediaminetetra(methylenephosphonic acid),tetramethylenediaminetetra(methylenephosphonic acid),hexamethylenediaminetetra(methylenephosphonic acid),diethylenetriaminepenta(methylenephosphonic acid), a salt of anyforegoing chelating agents (e.g., ethylenediaminetetraacetic aciddisodium salt dehydrate, ethylenediaminetetraacetic acid tetrasodiumsalt, nitrilotriacetic acid trisodium salt, sodium tripolyphosphate,sodium hexametaphosphate, etc.), and the like, and any combinationthereof.

Exemplary alkali metal bases may include, but are not limited to,lithium hydroxide, sodium hydroxide, potassium hydroxide, cesiumhydroxide, and the like, and any combination thereof.

In some embodiments, the treatment fluid may further comprisedispersants. Exemplary dispersants may include but are not limited to,betaines, sulfated or sulfonated alkoxylates, alkyl quaternary amines,alkoxylated linear alcohols, alkyl sulfonates, alkyl aryl sulfonates,C10-C20 alkyldiphenyl ether sulfonates, polyethylene glycols, ethers ofalkylated phenol, sodium dodecylsulfate, alpha olefin sulfonates (e.g.,sodium dodecane sulfonate), trimethyl hexadecyl ammonium bromide, andthe like, and any combination thereof. In some embodiments, thedispersant is present at about 0.1% to about 25% by weight of thetreatment fluid.

In some instances, the treatment fluid may be a cement slurry andfurther comprise one or more additives like a filler, a set accelerator,a set retarder, dispersants, and the like, and any combination thereof.Exemplary fillers may include but are not limited to, hollow ceramicbeads, ground marble, glass beads, crushed glass, polymer beads, and thelike, and any combination thereof. In some embodiments, the filler ispresent at about 0.1% to about 100% by weight of the cement (BWOC).Exemplary set accelerators may include but are not limited to, calciumchloride, triethanolamine, sodium silicate, zinc formate, calciumacetate, and the like, and any combination thereof. In some embodiments,the set accelerator is present at about 0.1% to about 5% BWOC. Exemplaryset retarders may include but are not limited to, tartaric acid,gluconic acid, carboxylic acids (e.g., citric acid), hydroxy carboxyacids, a sulfomethylated lignin, calcium lignosulfonates, sodiumlignosulfonates, copolymers of acrylic acid andacrylamido-methyl-propane sulfonate polymer, copolymers of maleicanhydride and acrylamido-methyl-propane sulfonate polymer, and the like,and any combination thereof. In some embodiments, the set retarder ispresent at about 0.1% to about 5% BWOC.

Some embodiments of downhole treating may involve introducing thetreatment fluid into a wellbore penetrating a subterranean formation.Exemplary downhole operations for implementing the treatment fluid ofthe present disclosure may include, but are not limited to, drillingoperations, drill-in operations, fracturing operations, gravel packingoperations, cementing operations, and the like.

For example, some embodiments may include forming a drilling fluiddescribed herein (e.g., mixing a water having hardness at about 300 ppmor greater with a plurality of particulates (e.g., comprising weightingagent and optionally cement), a swellable clay, a chelating agent, andan alkali metal base); and drilling at least a portion of a wellborepenetrating a subterranean formation with the drilling fluid.

In another example, some embodiments may include forming a drill-influid described herein (e.g., mixing a water having hardness at about300 ppm or greater with a plurality of particulates (e.g., comprisingweighting agent and optionally cement), a swellable clay, a chelatingagent, and an alkali metal base); and drilling at least a portion of awellbore into a production zone of a subterranean formation with thedrill-in fluid.

In yet another example, some embodiments may include forming afracturing fluid described herein (e.g., mixing a water having hardnessat about 300 ppm or greater with a plurality of particulates (e.g.,comprising proppant and optionally weighting agent), a swellable clay, achelating agent, and an alkali metal base); fracturing a portion of asubterranean formation (e.g., introducing the fracturing fluid or a padfluid before the fracturing fluid at a rate and pressure sufficient tocreate or extend at least one fracture in the subterranean formation);and forming a proppant pack comprising the proppant with the proppantfluid.

In another example, some embodiments may include forming a gravelpacking fluid described herein (e.g., mixing a water having hardness atabout 300 ppm or greater with a plurality of particulates (e.g.,comprising gravel and optionally weighting agent and/or cement), aswellable clay, a chelating agent, and an alkali metal base); andforming a gravel pack at least a portion of a wellbore and/or asubterranean formation with the gravel packing fluid.

In yet another example, some embodiments may include forming a cementslurry described herein (e.g., mixing a water having hardness at about300 ppm or greater with a plurality of particulates (e.g., comprisinggravel and optionally weighting agent and/or cement), a swellable clay,a chelating agent, and an alkali metal base); introducing the cementslurry into a wellbore penetrating a subterranean formation; and forminga set cement in at least a portion of the wellbore and/or thesubterranean formation with the cement slurry. For a primary cementingoperation, the cement slurry may be pumped into an annular space betweenthe walls of the wellbore and the casing and then allowed to set to forma cement sheath between the wellbore walls and the casing. Subsequentsecondary cementing operations may also be performed. One example of asecondary cementing operation is squeeze cementing whereby a cementslurry is employed to plug and seal off undesirable flow passages in thecement sheath and/or the casing.

Generally, a system for implementing the treatment fluids describedherein comprises a pump fluidly connected to a wellbore penetrating asubterranean formation that introduces treatment fluid into thewellbore.

In various embodiments, systems configured for delivering the treatmentfluids described herein to a downhole location are described. In variousembodiments, the systems can comprise a pump fluidly coupled to atubular, the tubular containing a treatment fluid described herein.

The pump may be a high pressure pump in some embodiments. As usedherein, the term “high pressure pump” will refer to a pump that iscapable of delivering a fluid downhole at a pressure of about 1000 psior greater. A high pressure pump may be used when it is desired tointroduce the treatment fluid to a subterranean formation at or above afracture gradient of the subterranean formation, but it may also be usedin cases where fracturing is not desired. In some embodiments, the highpressure pump may be capable of fluidly conveying particulate matter,such as proppant particulates, into the subterranean formation. Suitablehigh pressure pumps will be known to one having ordinary skill in theart and may include, but are not limited to, floating piston pumps andpositive displacement pumps.

In other embodiments, the pump may be a low pressure pump. As usedherein, the term “low pressure pump” will refer to a pump that operatesat a pressure of about 1000 psi or less. In some embodiments, a lowpressure pump may be fluidly coupled to a high pressure pump that isfluidly coupled to the tubular. That is, in such embodiments, the lowpressure pump may be configured to convey the treatment fluid to thehigh pressure pump. In such embodiments, the low pressure pump may “stepup” the pressure of the treatment fluid before it reaches the highpressure pump.

In some embodiments, the systems described herein can further comprise amixing tank that is upstream of the pump and in which the treatmentfluid is formulated. In various embodiments, the pump (e.g., a lowpressure pump, a high pressure pump, or a combination thereof) mayconvey the treatment fluid from the mixing tank or other source of thetreatment fluid to the tubular. In other embodiments, however, thetreatment fluid can be formulated offsite and transported to a worksite,in which case the treatment fluid may be introduced to the tubular viathe pump directly from its shipping container (e.g., a truck, a railcar,a barge, or the like) or from a transport pipeline. In either case, thetreatment fluid may be drawn into the pump, elevated to an appropriatepressure, and then introduced into the tubular for delivery downhole.

FIG. 1 shows an illustrative schematic of a system that can delivertreatment fluids of the present invention to a downhole location,according to one or more embodiments. It should be noted that while FIG.1 generally depicts a land-based system, it is to be recognized thatlike systems may be operated in subsea locations as well. As depicted inFIG. 1, system 100 may include mixing tank 110, in which a treatmentfluid of the present invention may be formulated. The treatment fluidmay be conveyed via line 112 to wellhead 114, where the treatment fluidenters tubular 116, tubular 116 extending from wellhead 114 intosubterranean formation 118. Upon being ejected from tubular 116, thetreatment fluid may subsequently penetrate into subterranean formation118.

In some instances, upon being ejected from tubular 116, the treatmentfluid may subsequently return up the wellbore in the annulus between thetubular 116 and the wellbore 122 as indicated by flow lines 124, forexample, in a cementing operation. In other embodiments, the treatmentfluid may be reverse pumped down through the annulus and up tubular 116back to the surface, for example, in a reverse cementing operation.

In some instances, tubular 116 may have a plurality of orifices 126through which the treatment fluid of the present disclosure may enterthe wellbore proximal to a portion of the subterranean formation 118 tobe treated, for example, in a fracturing operation or a gravel packingoperation.

In some instances, the wellbore may further comprise equipment or tools(not shown) for zonal isolation of a portion of the subterraneanformation 118 to be treated.

Pump 120 may be configured to raise the pressure of the treatment fluidto a desired degree before its introduction into tubular 116. It is tobe recognized that system 100 is merely exemplary in nature and variousadditional components may be present that have not necessarily beendepicted in FIG. 1 in the interest of clarity. Non-limiting additionalcomponents that may be present include, but are not limited to, supplyhoppers, valves, condensers, adapters, joints, gauges, sensors,compressors, pressure controllers, pressure sensors, flow ratecontrollers, flow rate sensors, temperature sensors, and the like.

Although not depicted in FIG. 1, the treatment fluid may, in someembodiments, flow back to wellhead 114 and exit subterranean formation118. In some embodiments, the treatment fluid that has flowed back towellhead 114 may subsequently be recovered and recirculated tosubterranean formation 118.

It is also to be recognized that the disclosed treatment fluids may alsodirectly or indirectly affect the various downhole equipment and toolsthat may come into contact with the treatment fluids during operation.Such equipment and tools may include, but are not limited to, wellborecasing, wellbore liner, completion string, insert strings, drill string,coiled tubing, slickline, wireline, drill pipe, drill collars, mudmotors, downhole motors and/or pumps, surface-mounted motors and/orpumps, centralizers, turbolizers, scratchers, floats (e.g., shoes,collars, valves, etc.), logging tools and related telemetry equipment,actuators (e.g., electromechanical devices, hydromechanical devices,etc.), sliding sleeves, production sleeves, plugs, screens, filters,flow control devices (e.g., inflow control devices, autonomous inflowcontrol devices, outflow control devices, etc.), couplings (e.g.,electro-hydraulic wet connect, dry connect, inductive coupler, etc.),control lines (e.g., electrical, fiber optic, hydraulic, etc.),surveillance lines, drill bits and reamers, sensors or distributedsensors, downhole heat exchangers, valves and corresponding actuationdevices, tool seals, packers, cement plugs, bridge plugs, and otherwellbore isolation devices, or components, and the like. Any of thesecomponents may be included in the systems generally described above anddepicted in FIG. 1.

FIG. 2, for example, illustrates a drilling system for implementing adrilling fluid and/or drill-in fluid 222 described herein. Asillustrated, the drilling assembly 200 may include a drilling platform202 that supports a derrick 204 having a traveling block 206 for raisingand lowering a drill string 208. The drill string 208 may include, butis not limited to, drill pipe and coiled tubing, as generally known tothose skilled in the art. A kelly 210 supports the drill string 208 asit is lowered through a rotary table 212. A drill bit 214 is attached tothe distal end of the drill string 208 and is driven either by adownhole motor and/or via rotation of the drill string 208 from the wellsurface. As the bit 214 rotates, it creates a borehole 216 thatpenetrates various subterranean formations 218.

A pump 220 (e.g., a mud pump) circulates drilling fluid or drill-influid 222 through a feed pipe 224 and to the kelly 210, which conveysthe drilling fluid or drill-in fluid 222 downhole through the interiorof the drill string 208 and through one or more orifices in the drillbit 214. The drilling fluid or drill-in fluid 222 is then circulatedback to the surface via an annulus 226 defined between the drill string208 and the walls of the borehole 216. At the surface, the recirculatedor spent drilling fluid or drill-in fluid 222 exits the annulus 226 andmay be conveyed to one or more fluid processing unit(s) 228 via aninterconnecting flow line 230. After passing through the fluidprocessing unit(s) 228, a “cleaned” drilling fluid or drill-in fluid 222is deposited into a nearby retention pit 232 (i.e., a mud pit). Whileillustrated as being arranged at the outlet of the wellbore 216 via theannulus 226, those skilled in the art will readily appreciate that thefluid processing unit(s) 228 may be arranged at any other location inthe drilling assembly 200 to facilitate its proper function, withoutdeparting from the scope of the scope of the disclosure.

One or more of the disclosed drilling fluids or drill-in fluids 222 maybe formed via a mixing hopper 234 communicably coupled to or otherwisein fluid communication with the retention pit 232. The mixing hopper 234may include, but is not limited to, mixers and related mixing equipmentknown to those skilled in the art. In other embodiments, however, thedisclosed drilling fluids or drill-in fluids 222 may be formed at anyother location in the drilling assembly 200. In at least one embodiment,for example, there could be more than one retention pit 232, such asmultiple retention pits 232 in series. Moreover, the retention pit 232may be representative of one or more fluid storage facilities and/orunits where the components of the drilling fluid or drill-in fluid 222may be stored, reconditioned, and/or regulated until added to thedrilling fluid or drill-in fluid 222.

As mentioned above, the disclosed drilling fluid or drill-in fluid 222may directly or indirectly affect the components and equipment of thedrilling assembly 200. For example, the disclosed drilling fluid ordrill-in fluid 222 may directly or indirectly affect the fluidprocessing unit(s) 228 which may include, but is not limited to, one ormore of a shaker (e.g., shale shaker), a centrifuge, a hydrocyclone, aseparator (including magnetic and electrical separators), a desilter, adesander, a separator, a filter (e.g., diatomaceous earth filters), aheat exchanger, any fluid reclamation equipment, The fluid processingunit(s) 228 may further include one or more sensors, gauges, pumps,compressors, and the like used store, monitor, regulate, and/orrecondition the drilling fluid or drill-in fluid 222.

The disclosed drilling fluid or drill-in fluid 222 may directly orindirectly affect the pump 220, which representatively includes anyconduits, pipelines, trucks, tubulars, and/or pipes used to fluidicallyconvey the drilling fluid or drill-in fluid 222 downhole, any pumps,compressors, or motors (e.g., topside or downhole) used to drive thedrilling fluid or drill-in fluid 222 into motion, any valves or relatedjoints used to regulate the pressure or flow rate of the drilling fluidor drill-in fluid 222, and any sensors (i.e., pressure, temperature,flow rate, etc.), gauges, and/or combinations thereof, and the like. Thedisclosed drilling fluid or drill-in fluid 222 may also directly orindirectly affect the mixing hopper 234 and the retention pit 232 andtheir assorted variations.

The disclosed drilling fluid or drill-in fluid 222 may also directly orindirectly affect the various downhole equipment and tools that may comeinto contact with the drilling fluid or drill-in fluid 222 such as, butnot limited to, the drill string 208, any floats, drill collars, mudmotors, downhole motors and/or pumps associated with the drill string208, and any MWD/LWD tools and related telemetry equipment, sensors ordistributed sensors associated with the drill string 208. The discloseddrilling fluid or drill-in fluid 222 may also directly or indirectlyaffect any downhole heat exchangers, valves and corresponding actuationdevices, tool seals, packers and other wellbore isolation devices orcomponents, and the like associated with the wellbore 216. The discloseddrilling fluid or drill-in fluid 222 may also directly or indirectlyaffect the drill bit 214, which may include, but is not limited to,roller cone bits, PDC bits, natural diamond bits, any hole openers,reamers, coring bits, etc.

While not specifically illustrated herein, the disclosed drilling fluidor drill-in fluid 222 may also directly or indirectly affect anytransport or delivery equipment used to convey the drilling fluid ordrill-in fluid 222 to the drilling assembly 200 such as, for example,any transport vessels, conduits, pipelines, trucks, tubulars, and/orpipes used to fluidically move the drilling fluid or drill-in fluid 222from one location to another, any pumps, compressors, or motors used todrive the drilling fluid or drill-in fluid 222 into motion, any valvesor related joints used to regulate the pressure or flow rate of thedrilling fluid or drill-in fluid 222, and any sensors (i.e., pressureand temperature), gauges, and/or combinations thereof, and the like.

It should be noted that while FIGS. 1-2 generally depicts a land-basedassemblies, those skilled in the art will readily recognize that theprinciples described herein are equally applicable to subsea operationsthat employ floating or sea-based platforms and rigs, without departingfrom the scope of the disclosure.

Embodiments described herein include, but are not limited to, EmbodimentA, Embodiment B, and Embodiment C.

Embodiment A is a treatment fluid comprising: a water having hardness atabout 300 ppm or greater; a plurality of particulates; a swellable clay;a chelating agent at about 0.01% to about 5% BWOW; and an alkali metalbase at about 0.01% to about 5% BWOW.

Embodiment A may optionally further include one or more of thefollowing: Element 1: wherein the treatment fluid is as drilling fluidand the plurality of particulates comprises weighting agents and/or acement and optionally wherein the cement (if present) comprises at leastone selected from the group consisting of: perlite, cement kiln dust,fly ash, pumicite, slag, lime, shale, and Portland cement; Element 2:wherein the treatment fluid is as fracturing fluid and the plurality ofparticulates comprises proppant; Element 3: wherein the treatment fluidis as cement slurry and the plurality of particulates comprises a cementand optionally wherein the cement comprises at least one selected fromthe group consisting of: perlite, cement kiln dust, fly ash, pumicite,slag, lime, shale, and Portland cement; Element 4: wherein the swellableclay comprises at least one selected from the group consisting of:beidellite, montmorillonite, bentonite, nontronite, saponite, naturallyoccurring hectorite clay, synthetic hectorite clay, palygorskite, andlasallite; Element 5: wherein the swellable clay is present at about0.1% to about 30% by weight of the treatment fluid; Element 6: whereinthe chelating agent comprises at least one selected from the groupconsisting of: ethylenediaminetetraacetic acid, nitrilotriacetic acid,diethylenetriaminepentaacetic acid,trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid, citric acid,diglycolic acid, phosphoric acid, aspartic acid, tripolyphosphate,hexametaphosphate, aminotris(methylenephosphonic acid),1-hydroxyethane-1,1-diphosphonic acid, dimethyl methylphosphonate,ethylenediaminetetra(methylenephosphonic acid),tetramethylenediaminetetra(methylenephosphonic acid),hexamethylenediaminetetra(methylenephosphonic acid),diethylenetriaminepenta(methylenephosphonic acid), and a salt of anyforegoing chelating agents; and Element 7: wherein the alkali metal basecomprises at least one selected from the group consisting of: lithiumhydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide.Exemplary combinations may include, but are not limited to, one ofElements 1-3 in combination with one or more of Elements 4-7; Elements 4and 5 in combination and optionally in further combination with Elements6 and/or 7; Elements 4, 6, and 7 in combination and optionally infurther combination with Element 5; and Elements 6 and 7 in combinationand optionally in further combination with Element 5.

Embodiment B is a system comprising: a pump fluidly connected to awellbore penetrating a subterranean formation that introduces atreatment fluid into the wellbore, wherein the treatment fluid is formedby mixing a water having hardness at about 300 ppm or greater with aplurality of particulates, a swellable clay, a chelating agent at about0.01% to about 5% BWOW, and an alkali metal base at about 0.01% to about5% BWOW.

Embodiment B may optionally further include one or more of thefollowing: Element 4; Element 5; Element 6; and Element 7. Exemplarycombinations may include, but are not limited to, Elements 4 and 5 incombination and optionally in further combination with Elements 6 and/or7; Elements 4, 6, and 7 in combination and optionally in furthercombination with Element 5; and Elements 6 and 7 in combination andoptionally in further combination with Element 5.

Embodiment C is a method comprising: mixing a water having hardness atabout 300 ppm or greater with a plurality of particulates, a swellableclay, a chelating agent at about 0.01% to about 5% BWOW, and an alkalimetal base at about 0.01% to about 5% BWOW to produce a treatment fluid;and introducing the treatment fluid into a wellbore penetrating asubterranean formation.

Embodiment C may optionally further include one or more of thefollowing: Element 4; Element 5; Element 6; Element 7; Element 8:wherein the treatment fluid is as drilling fluid and the plurality ofparticulates comprises weighting agents, and wherein the method furthercomprises drilling at least a portion of the wellbore with the drillingfluid; Element 9: wherein the treatment fluid is as fracturing fluid andthe plurality of particulates comprises proppant, and wherein the methodfurther comprises forming a proppant pack in at least a portion of thesubterranean formation with the fracturing fluid; Element 10: whereinthe treatment fluid is as drilling fluid and the plurality ofparticulates comprises a cement, and wherein the method furthercomprises drilling at least a portion of the wellbore with the drillingfluid; Element 11: wherein the treatment fluid is as cement slurry andthe plurality of particulates comprises a cement, and wherein the methodfurther comprises setting the cement slurry in at least a portion of thewellbore and/or the subterranean formation; Element 12: Element 11 andwherein the cement comprises at least one selected from the groupconsisting of: perlite, cement kiln dust, fly ash, pumicite, slag, lime,shale, and Portland cement; and Element 13: Element 12 and wherein thePortland cement comprises at least one selected from the groupconsisting of: Class A, Class C, Class H, Class G, ASTM Type III, andASTM Type V.

Exemplary combinations may include, but are not limited to, one ofElements 8-11 (with Element 11 optionally in combination with one orboth of Elements 12-13) in combination with one or more of Elements 4-7(e.g., Elements 4 and 5 in combination and optionally in furthercombination with Elements 6 and/or 7; Elements 4, 6, and 7 incombination and optionally in further combination with Element 5; andElements 6 and 7 in combination and optionally in further combinationwith Element 5).

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the present specification and associated claims areto be understood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired propertiessought to be obtained by the embodiments of the present invention. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claim, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

One or more illustrative embodiments incorporating the inventionembodiments disclosed herein are presented herein. Not all features of aphysical implementation are described or shown in this application forthe sake of clarity. It is understood that in the development of aphysical embodiment incorporating the embodiments of the presentinvention, numerous implementation-specific decisions must be made toachieve the developer's goals, such as compliance with system-related,business-related, government-related and other constraints, which varyby implementation and from time to time. While a developer's effortsmight be time-consuming, such efforts would be, nevertheless, a routineundertaking for those of ordinary skill in the art and having benefit ofthis disclosure.

While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methodscan also “consist essentially of” or “consist of” the various componentsand steps.

To facilitate a better understanding of the embodiments of the presentinvention, the following examples of preferred or representativeembodiments are given. In no way should the following examples be readto limit, or to define, the scope of the invention.

EXAMPLES Example 1

Seven cement slurries at a density of 10 lb/gal were produced accordingto Table 1 with different waters and chelating agent/alkali baseconcentrations according to Table 2.

TABLE 1 Component Unit of Measurement Quantity Class G Cement % BWOC 100FDP ™-C984-10 ¹ % BWOW 1.5 MICROBLOCK ™ ² gallons/sack 3 ECONOLITE ™Liquid ³ gallons/sack 1 D-AIR ™ 3000-L ⁴ gallons/sack 0.1 Water perTable 2 gallons/sack 40.56 ¹ a synthetic swellable clay available fromHalliburton Energy Services, Inc. ² silica powder available fromHalliburton Energy Services, Inc. ³ a cement set accelerator availablefrom Halliburton Energy Services, Inc. ⁴ a defoamer available fromHalliburton Energy Services, Inc.

TABLE 2 10 min Gel Water hardness Chelating Agent Alkali Base Strengthat Sample (ppm) (% BWOW) (% BWOW) 130° F. 1 50 — — 110 2 700 — — 25 3700 0.4 Fe⁻² — 20 4 700 0.4 HR-25 ™ ⁵ — 32 5 700 0.4 EDTA — 27 6 700 0.2EDTA — 31 7 700 0.2 EDTA 0.1 NaOH 103 ⁵ a high-temperatureretarder/intensifier available from Halliburton Energy Services, Inc.

Greater gel strengths indicate greater hydration of the swellable clay.As illustrated in this example, the inclusion of a small concentrationof an alkali base with a low concentration of chelating agent almostnegates the negative impact of the hard water.

Example 2

Four cement slurries at a density of 10 lb/gal were produced accordingto Table 1 with different waters and chelating agent/alkali baseconcentrations according to Table 2.

TABLE 3 Component Unit of Measurement Quantity Class G Cement % BWOC 100FDP ™-C984-10 % BWOW 1.5 Silicate gallons/sack 60 ECONOLITE ™ Liquidgallons/sack 0.8 D-AIR ™ 3000-L gallons/sack 0.05 Water per Table 4gallons/sack 55.75

TABLE 4 Water 10 min Gel hardness Chelating Agent Alkali Base Strengthat Sample (ppm) (% BWOW) (% BWOW) 150° F.  8 375 — — 20  9 375 0.15 EDTA0.05 NaOH 110 10 375 0.15 EDTA — 7 11 375 — 0.05 NaOH 45

Further, FIGS. 3-5 illustrate the properties of Sample 9. FIG. 3 is anon-off thickening plot where the slurry was sheared (stirred) for acertain amount of time followed by 15 static minutes. The shear/staticcycle was performed three times. When shear was initiated, there was aspike in the slurry consistency as measured in Bearden units ofconsistency (Bc), which indicates that the gel strength of the slurrywould build up in downhole conditions.

FIG. 4 is an ultrasonic cement analysis plot of the cement slurry thatmeasures the compressive strength of the slurry as it hardens. Withinabout 6 hours, Sample 9 developed a compressive strength of about 50psi, which illustrates that the combination of a chelating agent andalkali base helps develop a stable gel in hard water.

FIG. 5 a static gel strength plot of Sample 9. After stirring for 2hours, the slurry was kept static and analyzed. Within about 17 minutes,the slurry increased in static gel strength (SGS) by about 400 lb/100ft² (from about 100 lb/100 ft² to about 500 lb/100 ft²), whichillustrates that the combination of a chelating agent and alkali baseassists in quickly forming strong gels.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered,combined, or modified and all such variations are considered within thescope and spirit of the present invention. The invention illustrativelydisclosed herein suitably may be practiced in the absence of any elementthat is not specifically disclosed herein and/or any optional elementdisclosed herein. While compositions and methods are described in termsof “comprising,” “containing,” or “including” various components orsteps, the compositions and methods can also “consist essentially of” or“consist of” the various components and steps. All numbers and rangesdisclosed above may vary by some amount. Whenever a numerical range witha lower limit and an upper limit is disclosed, any number and anyincluded range falling within the range is specifically disclosed. Inparticular, every range of values (of the form, “from about a to aboutb,” or, equivalently, “from approximately a to b,” or, equivalently,“from approximately a-b”) disclosed herein is to be understood to setforth every number and range encompassed within the broader range ofvalues. Also, the terms in the claims have their plain, ordinary meaningunless otherwise explicitly and clearly defined by the patentee.Moreover, the indefinite articles “a” or “an,” as used in the claims,are defined herein to mean one or more than one of the element that itintroduces.

The invention claimed is:
 1. A cement slurry comprising: a water havinghardness of 300 ppm or greater with a plurality of particulates; cement;a swellable clay; a set accelerator; a defoamer; a chelating agent atabout 0.01% to about 5% by weight of the water (BWOW); and an alkalimetal base at about 0.01% to about 5% BWOW, wherein the chelating agentand alkali metal base reduce the negative effect of the water onhydrating swellable clays.
 2. The cement slurry of claim 1, wherein theswellable clay comprises at least one selected from the group consistingof: beidellite, montmorillonite, bentonite, nontronite, saponite,naturally occurring hectorite clay, synthetic hectorite clay,palygorskite, and lasallite.
 3. The cement slurry of claim 1, whereinthe swellable clay is present at about 0.1% to about 30% by weight of atreatment fluid.
 4. The cement slurry of claim 1, wherein the chelatingagent comprises at least one selected from the group consisting of:ethylenediaminetetraacetic acid, nitrilotriacetic acid,diethylenetriaminepentaacetic acid,trans-1,2-diaminocyclohexaneN,N,N′,N′-tetraacetic acid, citric acid,diglycolic acid, phosphoric acid, aspartic acid, tripolyphosphate,hexametaphosphate, aminotris(methylenephosphonic acid),1-hydroxyethane-1,1-diphosphonic acid, dimethyl methylphosphonate,ethylenediaminetetra(methylenephosphonic acid),tetramethylenediaminetetra(methylenephosphonic acid),hexamethylenediaminetetra(methylenephosphonic acid),diethylenetriaminepenta(methylenephosphonic acid), and a salt of anyforegoing chelating agents.
 5. The cement slurry claim 1, wherein thealkali metal base comprises at least one selected from the groupconsisting of: lithium hydroxide, sodium hydroxide, potassium hydroxide,and cesium hydroxide.
 6. The cement slurry of claim 1, wherein thecement comprises at least one selected from the group consisting of:perlite, cement kiln dust, fly ash, pumicite, slag, lime, shale, andPortland cement.
 7. The cement slurry of claim 6, wherein the Portlandcement comprises at least one selected from the group consisting of:Class A, Class C, Class H, Class G, ASTM Type III, and ASTM Type V. 8.The cement slurry of claim 1 further comprising a dispersant.
 9. Thecement slurry of claim 8, wherein the dispersant further comprisesbetaines, sulfated, sulfonated alkoxylates, alkyl quaternary amines,alkoxylated linear alcohols, alkyl sulfonates, alkyl aryl sulfonates,C10-C20 alkyldiphenyl ether sulfonates, polyethylene glycols, ethers ofalkylated phenol, sodium dodecylsulfate, alpha olefin sulfonates, sodiumdodecane sulfonate, trim ethyl hexadecyl ammonium bromide, and anycombination thereof.
 10. The cement slurry of claim 8, wherein thedispersant is present at about 0.1% to about 25% by weight of atreatment fluid.
 11. A cement slurry comprising: a water having hardnessat about 300 ppm with a plurality of particulates; a Portland cement; aswellable clay at about 0.1% to about 30% by weight of a treatmentfluid; a set accelerator at about 0.1% to about 5% by weight of cement;a defoamer; a chelating agent at about 0.01% to about 0.2% by weight ofthe water (BWOW); and an alkali metal base at about 0.01% to about 0.1%BWOW, wherein the chelating agent and alkali metal base reduce thenegative effect of the water on hydrating swellable clays.
 12. Thecement slurry of claim 11, further comprising a dispersant.
 13. Thecement slurry of claim 12, wherein the dispersant further comprisesbetaines, sulfated, sulfonated alkoxylates, alkyl quaternary amines,alkoxylated linear alcohols, alkyl sulfonates, alkyl aryl sulfonates,C10-C20 alkyldiphenyl ether sulfonates, polyethylene glycols, ethers ofalkylated phenol, sodium dodecylsulfate, alpha olefin sulfonates, sodiumdodecane sulfonate, trim ethyl hexadecyl ammonium bromide, and anycombination thereof.
 14. The cement slurry of claim 12, wherein thedispersant is present at about 0.1% to about 25% by weight of thetreatment fluid.
 15. A cement slurry comprising: a water having hardnessat about 300 ppm to about 6000 ppm with a plurality of particulates; aPortland cement; a swellable clay at about 0.1% to about 30% by weightof a treatment fluid; a set accelerator at about 0.1% to about 5% byweight of cement; a defoamer; a chelating agent at about 0.01% to about0.15% by weight of the water (BWOW); and an alkali metal base at about0.01% to about 0.05% BWOW, wherein the chelating agent and alkali metalbase reduce the negative effect of the water on hydrating swellableclays.
 16. The cement slurry of claim 15, wherein the chelating agent isethylenediaminetetraacetic acid (EDTA), and wherein the EDTA is presentin amount of 0.15% BWOW, and wherein the alkali metal base is sodiumhydroxide (NaOH), and wherein the NaOH is present in amount of 0.05%BWOW.
 17. The cement slurry of claim 15, wherein the Portland cementcomprises at least one selected from the group consisting of: Class A,Class C, Class H, Class G, ASTM Type III, and ASTM Type V.
 18. Thecement slurry of claim 15, further comprising a dispersant.
 19. Thecement slurry of claim 18, wherein the dispersant further comprisesbetaines, sulfated, sulfonated alkoxylates, alkyl quaternary amines,alkoxylated linear alcohols, alkyl sulfonates, alkyl aryl sulfonates,C10-C20 alkyldiphenyl ether sulfonates, polyethylene glycols, ethers ofalkylated phenol, sodium dodecylsulfate, alpha olefin sulfonates, sodiumdodecane sulfonate, trim ethyl hexadecyl ammonium bromide, and anycombination thereof.
 20. The cement slurry of claim 18, wherein thedispersant is present at about 0.1% to about 25% by weight of thetreatment fluid.